1. Field of the Invention
This invention relates to improvements in interferometer gyroscopes and, more particularly, to interferometer gyroscopes utilizing balanced heterodyne phase detection.
2. Description of the Prior Art
Interferometer gyroscopes, or gyros, are known in the art, as exemplified by the interferometer gyro described in U.S. Pat. No. 4,013,365.
In U.S. Pat. Ser. No. 936,680, filed Aug. 23, 1978 and entitled "Interferometer Gyro Using Heterodyne Phase Detection", said application being assigned to the assignee of the instant application, and being incorporated herein by reference, an interferometer gyro was disclosed which employs a balanced heterodyne phase detection system. The gyro employs a single laser source split into two components, each passed through an acousto-optic modulator to produce signal and reference light components. The signal component was split and injected in counter-rotating directions through a fiber solenoid or coil, then, the signals, after traversing the fiber optic coil, were mixed with the reference component to form a double heterodyne phase detecting system. Because the signal component is passed through the entire length of the optic fiber, but the reference component is not injected into the optic fiber at all, the source emission coherence length should be greater than the length of the fiber optic coil. This, in some applications, may constitute a relatively severe constraint upon the light source which can be employed.